Background
Phase 3, double-blind, placebo-controlled randomized trial (TOURMALINE-MM1). N=722 patients with relapsed or refractory multiple myeloma after 1–3 prior lines of therapy. Randomized 1:1. Key eligibility: ECOG PS ≤2; prior lenalidomide or pomalidomide permitted but not refractory to both; prior bortezomib allowed if not refractory.
Interventions and follow up
Arm A (IRd): Ixazomib 4 mg PO (days 1, 8, 15) + lenalidomide 25 mg PO (days 1–21) + dexamethasone 40 mg PO (days 1, 8, 15, 22), 28-day cycles until progression.
Arm B (placebo-Rd): Placebo PO (days 1, 8, 15) + lenalidomide 25 mg PO (days 1–21) + dexamethasone 40 mg PO (days 1, 8, 15, 22), 28-day cycles until progression.
Primary endpoint: Progression-free survival
Median follow-up: 23 months
Arm B (placebo-Rd): Placebo PO (days 1, 8, 15) + lenalidomide 25 mg PO (days 1–21) + dexamethasone 40 mg PO (days 1, 8, 15, 22), 28-day cycles until progression.
Primary endpoint: Progression-free survival
Median follow-up: 23 months
Results
mPFS: 20.6 vs 14.7 months, HR 0.74 (95% CI 0.59–0.94), P=.012
ORR: 78% vs 72%
≥CR rate: 11.7% vs 6.6%
OS: Not significantly different at primary or updated analyses
ORR: 78% vs 72%
≥CR rate: 11.7% vs 6.6%
OS: Not significantly different at primary or updated analyses
Adverse events
Hematologic (IRd vs placebo-Rd): Grade ≥3 thrombocytopenia 19% vs 9%; grade ≥3 neutropenia 23% vs 24%.
Neurologic: Peripheral neuropathy any grade 27% vs 22% (grade ≥3 2% vs 2%).
Dermatologic / GI: Rash any grade 36% vs 23% (grade ≥3 5% vs 2%); GI events (diarrhea, nausea, vomiting) increased with ixazomib but mostly low grade.
Neurologic: Peripheral neuropathy any grade 27% vs 22% (grade ≥3 2% vs 2%).
Dermatologic / GI: Rash any grade 36% vs 23% (grade ≥3 5% vs 2%); GI events (diarrhea, nausea, vomiting) increased with ixazomib but mostly low grade.
Conclusions
All-oral ixazomib added to Rd (IRd) significantly improved PFS (HR 0.74) in RRMM, providing the first all-oral proteasome-inhibitor-based triplet for myeloma and offering a convenient outpatient option without IV drug administration.
Key Limitations
The PFS benefit was modest (HR 0.74; absolute difference 5.9 months) and OS benefit was not demonstrated. The double-blind, placebo-controlled design appropriately controlled for bias, but the modest benefit raised questions about whether ixazomib adds clinically meaningful benefit over Rd alone. Lenalidomide-naïve patients were over-represented; generalizability to heavily pretreated lenalidomide-refractory patients is limited. Rash and GI toxicity are meaningful tolerability concerns.
Clinical Context
Ixazomib + Rd was FDA-approved in 2015 as the first all-oral proteasome inhibitor-based triplet regimen for RRMM, and is recognized in ASCO and ESMO relapse guidance. Its convenience (no infusion visits) is a key practical advantage. In the current era, IRd is primarily used in 1–2 prior line RRMM (lenalidomide-sensitive) or as maintenance therapy. Anti-CD38 triplets and carfilzomib-based regimens generally show greater efficacy.